Checklists of (1) surviving Italian harpsichords and virginals with split black keys; (2) similar instruments not known to survive but whose existence can be documented; (3) 26 Italian organs built during the period 1468-1665 that are known to have had split keys. Gives the ranges of these instruments when known. Discusses Frescobaldi's probable involvement with such instruments.
Wraight, Denzil and Stembridge, Christopher
"Italian split-keyboard instruments with fewer than nineteen divisions to the octave,"
Performance Practice Review:
2, Article 8.
Available at: https://scholarship.claremont.edu/ppr/vol7/iss2/8